1. Technical Field
The invention relates generally to the control of blood temperature during various operative procedures in which blood is introduced into a patient, and more particularly to a new and improved heat exchanger apparatus for this purpose.
2. Background Information
Blood temperature must be carefully controlled prior to introduction into a patient according to the operative procedure undertaken. In this regard, the blood may be heated to a desired temperature as high as thirty-seven degrees Centigrade, and it may be cooled to as low as five degrees Centigrade for some infant surgery. Heat is either added or withdrawn from the blood to accomplish this, and a heat exchanger performs this function.
The novel blood oxygenator heat exchanger described in the above-identified related applications is adapted to be inserted in an extracorporeal loop for this purpose. Blood from the patient passes through the apparatus and then back to the patient. As it flows through the apparatus it is oxygenated and brought to the desired temperature.
This is done with a heat exchanger tube wound into a helical coil through which a heat transfer fluid, such as water, is passed. The tube is disposed between two surfaces and employs a bellows configuration, i.e., a plurality of individual external ribs on the heat exchanger tube, that result in the tube having reduced cross-sectional area regions between the ribs. Each of the inner and outer surfaces is scalloped to define generally vertical passages along the reduced cross-sectional area regions between adjacent windings of the coil. Blood flows from an oxygenator arrangement along a generally vertical, gently undulating blood flow path through the reduced cross-sectional area regions, and this results in the exchange of heat between the blood and the heat transfer fluid.
There are some aspects that could be further refined, however. For example, a heat exchanger apparatus with less complicated, and correspondingly less costly, structure is desirable. Also, it is sometimes desirable to employ a cardiotomy filter in operative procedures in which the heat exchanger is used. Thus, it would be desirable to have an apparatus adapted to receive such a filter, in order to have a compact, multifunction, blood processing station.
In addition, it is sometimes desirable to bring blood to a desired temperature apart from oxygenating or otherwise processing the blood. Preheating donor blood for rapid blood infusion provides an example. Thus, it is desirable to have a stand alone heat exchanger apparatus that can be used for this limited purpose.